Electric timepiece

ABSTRACT

This invention relates to an electric timepiece containing a mechanical contact actuated by the movement of the balance wheel together with the electronic circuit combined thereto, in which the pallet is electromagnetically driven by said electronic circuit, to drive said balance wheel mechanically and to rotate the escapement wheel to drive the gear trains engaging with the escapement wheel so as to make time-display.

Umted States Patent 1 [111 3,745,759

Kurosawa July 17, 1973 1 ELECTRIC TIMEPIECE 3,066,474 12/1962 Detwiler 58/28 R [75] Inventor: Moriyoshi Kurosawa, Funabashi-shi, 2 31: 22 235 g Chiba Japan [73 Assi nee: Kabushiki Knish D i i k h 1 g a a n 05 Primary Examiner-Richard B. Wilkinson Tokyo, Japan Assistant Examiner-Edith C. Simmons Jackmon [22] Filed: Nov. 13, 1970 Attorney-mum, Moscovitz, Friedman & Kapian [21] Appl. No.: 89,231

[30] Foreign Application Priority Data [57] ABSTRACT Dec. 8, 1969 Japan 44/9780] This invention relates to an electric timepiece i ing a mechanical contact actuated by the movement of g 58/28 58/23 318/131 the balance wheel together with the electronic circuit [58] id G04: 3/04 combined thereto, in w i the ll i electromagnet 0 58/23 23 28 ically driven by said electronic circuit, to drive said bal- 28 28 3 116 M1; 318/131 ance wheel mechanically'and to rotate the escapement wheel to drive the gear trains engaging with the escape- [56] References C'ted ment wheel so as to make time-display.

UNITED STATES PATENTS R26,187 8 Claims, 8 Drawing Figures 3/1967 Horn et al 58/28 R PATENTED JUL-1 3. 745 759 sum 1 or 4 PATENTEU JUL] 7 3. 745 759 sum 2 0F 4 ELECTRIC TIMEPIECE BACKGROUND OF THE INVENTION This invention relates to an electric timepiece with a mechanical contact and more particularly to an electric timepiece containing a mechanical contact actuated by the oscillation of the balance wheel and an electronic circuit to drive the pallet electromagnetically.

In the conventional devices in which the pallet is directly driven electromagnetically and drives the balance wheel mechanically a transistor provided in the electronic circuit is activated by a detecting voltage generated in a detecting coil in response to the movement of the pallet, and its output current flows in the driving coil and drives the pallet electromagnetically.

As is generally known, an input voltage of at least 0.5 0.7 volts is necessary to activate a transistor. In comparison with the amplitude of the balance wheel which is about 270", that of the pallet is much smaller (approximately Further, the speed of rotation of the pallet is much smaller than that of the balance wheel. Therefore, it is difficult to generate sufficient detecting voltage in response to the rotation of the pallet. Because of this factor, a detecting coil having 20,000 to 30,000 turns is used, which is the maximum value permissible in the space of the watch movement.

The magnetic circuit must not only detect but provide the driving and traction of the pallet. In particular, the slightest variation of the dimensions of the magnetic gap causes variations of the self-inductance, mutual inductance and coupling factor of the detecting coil and the driving coil. Accordingly, it is necessary to re-select the time constant or the constant of the transistor, diode, condenser and resistor which constitute the electronic circuit. In addition, said variation in the dimension of the gap also seriously affects the traction or driving force for lateral positioning of the pallet, i.e., the magnetic circuit exerts very complex influences on the detecting voltage, constant of the electronic circuit, amplitude of the balance wheel and balancing of the traction force of the pallet. Accordingly, the tolerance of the magnetic gap, which is the most important portion in the magnetic circuit, is only 2 5 microns, the adjustment of the magnetic gap being very difficult and inefficient. As a result, mass-production of timepieces, and low cost, cannot be realized.

Further, in case of decomposition and cleaning of the timepiece, it is very difficult to reproduce the various characteristics such as amplitude characteristics, characteristics of electronic circuit and those of the magnetic circuit and equilibrium of traction force.

BRIEF DESCRIPTION OF THE INVENTION The subject matter of the present invention is to provide an electric timepiece having the following construction and operation to eliminate the abovementioned difiiculties.

A permanent magnet fixed to the pallet is disposed in the circular air gap of the yoke with two pairs of magnetic poles. Said yoke has a triangular form, one of its sides being wound by the driving coil. When the balance wheel oscillates, the second roller jewel on the roller of the balance wheel closes the contact and a high input voltage is supplied to a class B amplifier circuit with a transistor. This contact is provided with a damper to prevent the oscillation of a contact spring when the contact is opened. The output current of said electronic circuit is applied to said driving coil and magnetizes two pairs of magentic poles. The permanent magnet fixed on the pallet and two pairs of magnetic poles attract and repulse each other, thereby driving the pallet. The pallet fork gives an impulse to the first roller jewel of the balance wheel and drives the balance wheel.

On the other hand, the pallet jewels rotate the escape wheel and drive the gear trains engaged with the latter to make the time-display.

As stated above, in this driving device for the balance wheel, activation of the transistor is completely separated from the driving and traction of the pallet.

Therefore, one of the objects of the present invention is to provide an electric timepiece in which detection is effected by a mechanical contact without any detecting coil.

Another object of the present invention is to provide a stable electric timepiece in which the detecting voltage is independent from the amplitude of the balance wheel, the amplitude of the balance wheel being rapidly restored to the predetermined value when the bal' ance wheel is started or when the amplitude of the balance wheel is decreased by shocks.

Another object of the present invention is to provide an electric timepiece with a damper to prevent the parasitic oscillation of the contact caused by external shocks.

A further object of the present invention is to provide an electric timepiece in which the current flowing through the contact is reduced to the minimum to prevent stain or adhesion of the contact pieces caused by sparking.

A still further object of the present invention is to provide an electric timepiece in which the adjustment of the traction force of the pallet is not necessary and which is easily mounted, regulated, decomposed and cleaned.

Another object of the present invention is to provide an easily manufactured, low cost, electric timepiece suitable for mass production.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plain view of an embodiment of the present invention;

FIG. 2 is a partial cross-sectional view of FIG. 1;

FIG. 3 is an enlarged view of the contact part;

FIG. 4 shows the electric circuit diagram;

FIG. 5 shows the electric waveform of the contact;

FIG. 6 is another embodiment of the electronic circuit; and

FIG. 7 shows another embodiment of the electric cir-. cuit.

DESCRIPTION OF EMBODIMENTS Referring more particularly to FIG. I and 2 of the 5 companying drawings, the balance wheel 1 comprises a balance wheel 2 made of brass, a balance staff 3, a collet 4, a roller 5, the first roller jewel 6 and the second roller jewel 7 mounted on the roller 5 and a hairspring which can oscillate in a constant period. Pallet 14 comprises non-magnetic pallet 15, pallet staff 17, permanent magnet 16 fixed on said pallet staff 17, in parallel with said pallet 15, and pallet jewels 18a and 18b fixed respectively on the ends 15a and 15b of the pallet 15. The pallet 14 is supported on a hole jewel 24a fixed to the pallet cock 22 and on a hole jewel 24b fixed to plate 23. Pallet jewels 18a and 18b engage with escape wheel 25, which in turn engages with the train wheels (not shown) to rotate the hands. n the other hand, pallet fork c engages with the first roller jewel 6 todrive balance wheel I. Said permanent magnet 16 is positioned within circular space 21 for magnetic engagement with four magnetic poles 19a, 19b, a and 20b and a pair of magnetic paths 26 and 27 of yoke 28. Particularly, said permanent magnet 16 and magnetic poles 19a, 19b, 20a and 20b are disposed so as to define a narrow space between them. A driving coil 29 is wound on a part of yoke 28. This yoke 28 has a triangular form which is made of magnetic paths 26, 27 and driving coil 29 and fixed on the plate 23 by means of 20 screws 30a, 30b, 33 and 34.

As shown on an enlarged scale in FIG. 3, said second roller jewel 7 engages with an elastic contact spring 9 and allows it to touch contact pin 11. Said contact spring 9 and a damper 9a with a bent end interfering lightly with contact spring 9 are fixed on a holder pin '10 to prevent undesirable chattering of said contact spring 9 and said contact pin 11 which may be caused when contact spring 9 is disengaged from said roller jewel 7. On the other hand, said holder pin 10 and said contact pin 11 are mounted on printed board 12 and connected to the external electronic circuit through thin film patterns made of copper 13a and 13b which are attached on the surfaces of the above-mentioned pins. Said printed board 12 is fixed on plate 23 by means of screws 31 and 32.

In the electronic circuit as shown in FIG. 4, contact pin 1 l is connected to the base of transistor 36 through resistor 35 which has a high resistance value of the order of 100 K0, while contact spring 9 is connected to the plus electrode of battery 40. Emitter 38 is connected to the minus electrode of battery 40. One end of said driving coil 29 is connected to collector 39 and further, diode 41 is connected to driving coil 29 in parallel.

The operation of this invention is as follows:

As shown in FIG. 1, when balance wheel 1 rotates in a clockwise direction as shown by the arrow 47, the second roller jewel 7 pushes contact spring 9 and the latter touches contact pin 11. The electronic circuit constituted from battery 40, said contact spring 9, contact pin 11, resistor 35, base 37 and emitter 38 is then closed and a base current iof a i, of value as shown in FIG. 5 a flows. This current is very feeble, of several micro amperes, for example, because the voltage of the battery-is 1.5 volts. This current, however, is sufi'icient for switching of the transistor 36 and the voltage between collector 39, emitter 38 becoming practically zero. An output current i of the order of 100 micro arnperes having a rising characteristic as shown in FIG. 5 b then flows in driving coil 29. This output current generates a magnetic flux in the magnetic paths 26 and 27 in the direction of the arrows 42 and 43, and magnetizes said magnetic poles 19a and 20a to N pole and said magnetic poles 19b and 20b to S pole. As a result, magnetic action is generated between these magnetic poles and N and S poles of the permanent magnet 16.

The same type of poles repulse each other and the different type of poles attract each other. Accordingly, pallet 14 is driven rotationally in the counter-clockwise direction as shown by the arrow 44, pallet fork being displaced rapidly from the position of banking pin 45 to the position of banking pin 46.

The first roller jewel 6 and' pallet fork 150 is so dis-- posed that the first roller jewel 6 begins to engage with pallet fork 15c at the moment the second roller jewel 7 begins to engage with contact spring 9. Accordingly, the first roller jewel is kicked strongly at the same time that said pallet 14 is driven rotationally to the direction of the arrow 44. As a result, balance wheel 1 is rotated mechanically in the direction of the arrow 47.

When the second roller jewel 7 passes over the position of contact spring 9, shown by the dotted line, and disengages from contact spring 9, said contact spring 9 separates from contact pin 11, transistor 36 is turned off, the driving current stops and N and S of the magnetic poles 19a, 19b, 20a and 20b disappear.

On the other hand, traction force is necessary to attract pallet 15 to banking pin 45. Even if said magnetic poles 19a, 19b, 20a and 20b have disappeared, the N pole of permanent magnet 16 and magnetic pole 20a, and the S pole of permanent magnet 16 and magnetic pole 19b respectively attract each other. Therefore, it is possible to settle pallet 14 stably to banking pin 45.

As the change of the relative position of permanent magnet 16, magnetic poles 19a, 19b, 20a and 20b do not influence the operation of the electronic circuit, it is not necessary to strictly adjust their relative position. Accordingly, the magnetic circuit can be fixed previously to the plate by means of screws 30a and 30b which are provided on the magnetic paths 26 and 27 respectively and no adjustment of traction force is needed.

Next, when balance wheel 1 rotates in the opposite direction and the second roller jewel 7 moves in the opposite direction to arrow 47, the second roller jewel 7 only grazes the end of contact spring 9 slightly and does not provide any action upon the latter. The first roller jewel 6 returns pallet 14 from the side of banking pin 46 to the side of banking pin 45, said contact spring 9 and contact pin 11 remaining separated and said transistor 36 also remaining off. Diode 41 is provided to prevent degradation or rupture of the transistor 36 caused by a large counter electromotive force which tends to be generated when transistor 36 turns off. It is possible to eliminate this diode 41 by using a transistor which has high tension resistivity.

Further, when the second roller jewel 7 disengages from contact spring 9 at the position of the dotted line, contact spring 9 begins self oscillation. Dimensions and strength of damper 9a is selected so that contact spring 9 may not push aside damper 9a and touch contact pin 11. Forexample, by making damper 9a interfere with contact spring 9 at the center part thereof where contact spring 9 is designated to engage with contact pin 11 and making the natural frequency of damper 9a three to five times higher than that of contact spring, self oscillation of said contact spring attenuates rapidly and chattering of contact spring 9 and contact pin 11 can be prevented effectively. At the same time it is possible to prevent unnecessary oscillation of contact spring 9 caused by-the external shocks which it suffers while the watch is being worn.

Further, when pallet 14 moves from side to side between banking pins 45 and 46, pallet jewels 18a and 18b alternately push the inclined faces of the teeth of escape wheel 25 one by one and drive the latter rotationally in the direction of the arrow 48. Said escape wheel 25 engages with the train wheel (not shown) and can rotate second, minute and hour hands correctly.

FIG. 6 shows the other embodiment of the damper. This is damper 9b made of a very thin plate instead of damper 9a which is made of wire. This damper 9b can be manufactured, mounted and adjusted with relative ease. It is also clear that damper 9b can effect quite the same action as that of damper 9a.

FIG. 7 shows the other embodiment of the electronic circuit which uses MOS transistor 49. As is commonly known, a MOS transistor has a very high input impedance which can be dealt with as infinite in practice. Therefore, this electronic circuit does not need resistor 35, and contact pin 11 can be connected directly to gate 50. Source 51 of enhancement type MOS transistor 49 is connected to the minus electrode of battery 40 and its drain 52 to driving coil 29. When contact spring 9 touches contact pin 11, the voltage of gate 50 becomes the same as that of plus voltage battery 40, and said MOS transistor can be switched on to the deeply saturated cg ondition. As a result, an output current with quite the same wave form as that shown in FIG. 5 0 flows in driving coil 29. In this way pallet 14 and balance wheel 1 can be driven in the same way as described above.

While a preferred form of the invention has been disclosed in the foregoing specification and accompanying drawings, other modifications and substitutions of equivalents will occur to those skilled in the art after a study of the disclosure of the present invention without departing from the spirit and scope of said invention. Hence, the description should be taken in an illustrative rather than a limiting sense.

What is claimed 1. An electric timepiece comprising a balance wheel provided with a first roller jeweland a second roller jewel and oscillating in a constant cycle; a pallet having a pallet fork positioned to strike intermittently against said first roller jewel to drive said balance wheel; an escape wheel positioned for driving by said pallet; a permanent magnet fixed coaxially to said pallet; a magnetic yoke having a driving coil extending thereabout and defining a magnetic circuit positioned to cooperate with said permanent magnet to position said permment magnet, and therefore said pallet, upon the application of driving current to said driving coil; driving circuit means including said driving coil, transistor means having said driving coil connected in series with the emitter-collector path thereof, and base circuit means connected to the base of said transistor and including resistor means, an elastic contact spring positioned in the path of displacement of said second roller jewel for engagement and displacement thereby when said first roller jewel engages with the pallet fork of said pallet, and a contact pin positioned in the path of displacement of said elastic contact spring for engagement thereby to close said base circuit means to apply said driving current to said driving coil to drive said pallet to rotate said balance wheel; and damper means for damping the oscillation of said elastic contact spring when said contact spring is disengaged from said contact pin.

2. An electric timepiece according to claim 7, wherein said damper means is formed of wire.

3. An electric timepiece according to claim 7, wherein said damper means is formed from a thin plate fixed at one end and engaging said contact spring at the other end thereof.

4. An electric timepiece according to claim I, wherein said yoke has a triangular form.

5. An electric timepiece comprising a balance wheel provided with a first roller jewel and a second roller jewel and oscillating in a constant cycle; a pallet having a pallet fork positioned to strike intermittently against said first roller jewel to drive said balance wheel; an excape wheel positioned to be driven by said pallet; a permanent magnet fixed coaxially to said pallet; a magnetic yoke having a driving coil extending thereabout for defining a magnetic circuit positioned to cooperate with said permanent magnet to position said permanent magnet in response to driving current applied to said driving coil; driving circuit means including said driving coil, a MOS transistor connected with its source-drain path in series with said driving coil; and gate circuit means connected to the gate of said MOS transistor including an elastic contact spring positioned for engagement and displacement by said second roller jewel when said first roller jewel engages said pallet fork of said pallet, and a contact pin positioned in the path of displacement of said elastic contact spring for engagement thereby to close said gate circuit means to apply said driving current to said driving coil to drive said pallet for rotating said balance wheel; and damper means positioned to engage said elastic contact spring to dampen the oscillation thereof after said contact spring is disengaged from said contact pin.

6. An electronic timepiece according to claim 5, wherein said magnetic yoke has a triangular form.

7. An electric timepiece according to claim 1, wherein said damper means engages said contact spring at the center part thereof in the region where said contact spring engages with said contact pin and has a natural frequency three to five times higher than that of said contact spring.

8. An electric timepiece according to claim 1, wherein said yoke has a circular space in which said permanent magnet fixed to said pallet is located and two pairs of magnetic poles for traction and repulsion of said permanent magnet.

# t t i I 

1. An electric timepiece comprising a balance wheel provided with a first roller jewel and a second roller jewel and oscillating in a constant cycle; a pallet having a pallet fork positioned to strike intermittently against said first roller jewel to drive said balance wheel; an escape wheel positioned for driving by said pallet; a permanent magnet fixed coaxially to said pallet; a magnetic yoke having a driving coil extending thereabout and defining a magnetic circuit positioned to cooperate with said permanent magnet to position said permanent magnet, and therefore said pallet, upon the application of driving current to said driving coil; driving circuit means including said driving coil, transistor means having said driving coil connected in series with the emitter-collector path thereof, and base circuit means connected to the base of said transistor and including resistor means, an elastic contact spring positioned in the path of displacement of said second roller jewel for engagement and displacement thereby when said first roller jewel engages with the pallet fork of said pallet, and a contact pin positioned in the path of displacement of said elastic contact spring for engagement thereby to close said base circuit means to apply said driving current to said driving coil to drive said pallet to rotate said balance wheel; and damper means for damping the oscillation of said elastic contact spring when said contact spring is disengaged from said contact pin.
 2. An electric timepiece according to claim 7, wherein said damper means is formed of wire.
 3. An electric timepiece according to claim 7, wherein said damper means is formed from a thin plate fixed at one end and engaging said contact spring at the other end thereof.
 4. An electric timepiece according to claim 1, wherein said yoke has a triangular form.
 5. An electric timepiece comprising a balance wheel provided with a first roller jewel and a second roller jewel and oscillating in a constant cycle; a pallet having a pallet fork positioned to strike intermittently against said first roller jewel to drive said balance wheel; an excape wheel positioned to be driven by said pallet; a permanent magnet fixed coaxially to said pallet; a magnetic yoke having a driving coil extending thereabout for defining a magnetic circuit positioned to cooperate with said permanent magnet to position said permanent magnet in response to driving current applied to said driving coil; driving circuit means including said driving coil, a MOS transistor connected with its source-drain path in series with said driving coil; and gate circuit means connected to the gate of said MOS transistor including an elastic contact spring positioned for engagement and displacement by said second roller jewel when said first roller jewel engages said pallet fork of said pallet, and a contact pin positioned in the path of displacement of said elastic contact spring for engagement thereby to close said gate circuiT means to apply said driving current to said driving coil to drive said pallet for rotating said balance wheel; and damper means positioned to engage said elastic contact spring to dampen the oscillation thereof after said contact spring is disengaged from said contact pin.
 6. An electronic timepiece according to claim 5, wherein said magnetic yoke has a triangular form.
 7. An electric timepiece according to claim 1, wherein said damper means engages said contact spring at the center part thereof in the region where said contact spring engages with said contact pin and has a natural frequency three to five times higher than that of said contact spring.
 8. An electric timepiece according to claim 1, wherein said yoke has a circular space in which said permanent magnet fixed to said pallet is located and two pairs of magnetic poles for traction and repulsion of said permanent magnet. 